Temperature dependence of exchange bias in polycrystalline ferromagnet-antiferromagnet bilayers
Temperature dependence of exchange bias in polycrystalline ferromagnet-antiferromagnet bilayers
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DOI：
10.1103/physrevb.60.12950
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发表时间：
1999-11
影响因子：
3.7
通讯作者：
M. Stiles;R. McMichael
中科院分区：
文献类型：
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作者：
M. Stiles;R. McMichael
我们描述了一个简单的模型的交换偏置的温度依赖性和相关的影响，导致耦合铁磁薄膜的多晶反铁磁膜。在这个模型中，温度依赖性的一个重要来源来自反铁磁颗粒中反铁磁态的热不稳定性，就像超顺磁性颗粒中发生的那样。在足够低的温度下，每个晶粒中的反铁磁状态是稳定的铁磁磁化旋转和模型预测的单向各向异性，引起所观察到的交换偏置环路移位。在较高的温度下，反铁磁态在短时间尺度上保持稳定，但在较长的时间尺度上，由于热激发超过能垒而变得不稳定。对于这些温度下，该模型预测的高场旋转的转矩实验中发现的磁滞和铁磁共振测量中发现的各向同性场移位。
We describe a simple model for the temperature dependence of the exchange bias and related effects that result from coupling a ferromagnetic thin film to a polycrystalline antiferromagnetic film. In this model, an important source of temperature dependence comes from thermal instabilities of the antiferromagnetic state in the antiferromagnetic grains, much as occurs in superparamagnetic grains. At low enough temperatures, the antiferromagnetic state in each grain is stable as the ferromagnetic magnetization is rotated and the model predicts the unidirectional anisotropy that gives rise to the observed exchange-bias loop shift. At higher temperatures, the antiferromagnetic state remains stable on short time scales, but on longer time scales, becomes unstable due to thermal excitations over energy barriers. For these temperatures, the model predicts the high field rotational hysteresis found in rotational torque experiments and the isotropic field shift found in ferromagnetic resonance measurements.